1. Field of the Invention
This invention generally relates to methods for determining one or more properties of an insulating film. Certain embodiments relate to methods for determining hysteresis of an insulating film without contacting the insulating film.
2. Description of the Related Art
Fabricating semiconductor devices such as logic and memory devices may typically include processing a substrate such as a semiconductor wafer using a number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. For example, insulating (or dielectric) films may be formed on multiple levels of a substrate using deposition processes such as chemical vapor deposition (xe2x80x9cCVDxe2x80x9d), physical vapor deposition (xe2x80x9cPVDxe2x80x9d), and atomic layer deposition (xe2x80x9cALDxe2x80x9d). In addition, insulating films may be formed on multiple levels of a substrate using a thermal growth process. For example, a layer of silicon dioxide may be thermally grown on a substrate by heating the substrate to a temperature of greater than about 700xc2x0 C. in an oxidizing ambient such as O2 or H2O. Such insulating films may electrically isolate conductive structures of a semiconductor device formed on the substrate.
Measuring and controlling such insulating films may be an important aspect of semiconductor device manufacturing. A number of techniques are presently available for measuring hysteresis of insulating films. For example, electrical measurement techniques that rely on physical contact to a conductive electrode on top of an insulating film are able to determine hysteresis properties of insulating films using capacitance vs. voltage (C-V) and current vs. voltage (I-V) measurements. Such measurements have a long history and established utility.
Examples of physically contacting techniques that can be used to extract hysteresis measurements include depositing or growing the insulating film under test on a semiconducting or metallic substrate. In a first example, an electrode is deposited on top of the film under test, and the area of the electrode defines the area of measurement. A metal probe is placed in contact with a metal or polysilicon electrode, and an electrical bias is applied through the probe. In another example, a temporary electrode is lowered until it is in contact with the film under test. The electrode may be a conducting liquid (e.g., mercury), a conducting polymer, or any material that exhibits sufficiently conductive behavior. The area of the temporary electrode defines the area of measurement. An electrical bias is applied through the temporary electrode.
However, these measurements require a conductive electrode and a contacting probe. The necessity of direct physical electrical contact is particularly undesirable in many manufacturing situations. Accordingly, it would be advantageous to develop a method for measuring hysteresis without direct physical electrical contact.
An embodiment of the invention relates to a non-contact method for determining a property of an insulating film. The method includes measuring an amount of hysteresis in the insulating film without contacting the insulating film. The method also includes determining the amount of hysteresis in the insulating film. In one embodiment, the method may further include monitoring a presence of voids in the insulating film using the amount of hysteresis. The amount of hysteresis in the insulating film may be responsive to the presence of voids in the insulating film. In one such embodiment, the insulating film may be a low-k insulating film. In another such embodiment, the insulating film may be a high-k insulating film. In an additional embodiment, the method may include monitoring a presence of traps in the insulating film using the amount of hysteresis. The amount of hysteresis in the insulating film may be responsive to the presence of traps in the insulating film. In one such embodiment, the insulating film may be a thermally grown film. In another such embodiment, the insulating film may be a high-k insulating film. In a further embodiment, the method may include monitoring a presence of voids in the insulating film and a presence of traps in the insulating film using the amount of hysteresis.
In another embodiment, the insulating film may include a thermally grown film. In such an embodiment, the method may include processing the thermally grown film prior to measuring the amount of hysteresis. Therefore, the amount of hysteresis may be responsive to traps in the thermally grown film that may have been caused by the processing. In one embodiment, the method may also include processing the insulating film after formation of the insulating film and prior to measuring the amount of hysteresis. In this embodiment, the amount of hysteresis may be responsive to damage of the insulating film caused by the processing. In one example, the processing may include a plasma process.
In some embodiments, measuring the amount of hysteresis may include measuring an electrical characteristic of the insulating film before and after applying an electrical field to the insulating film. The electrical field may be applied for a period of time. In other embodiments, measuring the amount of hysteresis in the insulating film may include stressing the insulating film by applying an electrical field to the insulating field, by heating the insulating film, or by applying ultraviolet light to the insulating film. In one such embodiment, measuring the amount of hysteresis may also include measuring an electrical characteristic of the insulating film before and after stressing of the insulating film.
In one embodiment, the method may further include measuring one or more other properties of the insulating film. In addition, the method may include determining the one of more other properties of the insulating film from the measurements. In another embodiment, the insulating film may include an oxide. In such an embodiment, the method may include measuring trace metals in the oxide and determining an amount of the trace metals in the oxide. The method may include additional steps as described herein.
Another embodiment relates to a computer-implemented method for data analysis. The method includes determining a single numeric value representing an amount of hysteresis in an insulating film from electrical characteristics of the insulating film. The electrical characteristics are measured without contacting the insulating film. In one embodiment, the electrical characteristics of the insulating film are measured before and after application of an electrical field to the insulating film. The electrical field is applied to the insulating film without contacting the insulating film. In another embodiment, the method may include analyzing a bulk charge trap density in the insulating film using the single numeric value determined above. In an additional embodiment, the method may include analyzing polarization effects of voids in the insulating film using the single numeric value determined above. In a further embodiment, the method may include analyzing damage of the insulating film using the single numeric value representing the amount of hysteresis in the insulating film. In one such embodiment, the damage may be caused by processing of the insulating film performed after formation of the insulating film. The method may include additional steps as described herein.
An additional embodiment relates to a system that includes a measurement system and a computer-usable carrier medium. The measurement system is configured to measure an amount of hysteresis in an insulating film without contacting the insulating film. The carrier medium includes program instructions. The program instructions are executable on a computer system for determining the amount of hysteresis in the insulating film using measurements from the measurement system. The system may be further configured as described herein.